This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The primary goal of this study was to test the hypothesis that tick saliva, in the context of Borrelia burgdorferi, can have widespread effects on both the genomic profile of immune pathways associated with skin cells such as monocytes/macrophages and fibroblasts and on the subsequent protein expression associated with those pathways by examining the in vitro effects of tick saliva on human monocytes during their co-culture with B. burgdorferi. The prolonged feeding process of ixodid ticks, in combination with bacterial transmission, should lead to a robust inflammatory response at the blood-feeding site. Yet, factors present in tick saliva may down-regulate such deleterious responses. Transcripts and/or supernatants isolated from human THP-1 monocytes stimulated with B. burgdorferi and grown in the presence or absence of tick saliva were used in human microarray, cytokine bead array, ELISA, and qRT-PCR experiments. Monocyte RNA harvested from three time points during co-culture with B. burgdorferi and saliva illustrated that saliva can have a suppressive effect on the expression of certain pro-inflammatory mediators, such as IL-8 and TLR-2 as well as have a stimulatory effect on specific molecules such as IL-10ra, a known mediator of the immunosuppressive signal of IL-10. Supernatants were analyzed via antigen-capture ELISA and cytokine bead array for inflammatory mediator production. Treatment with saliva significantly reduced the expression of several key mediators including IL-6, IL-8 and TNF-alpha by THP-1 monocytes. Similar experiments were conducted using primary rhesus fibroblasts and our results indicate that tick saliva has an opposite effect on these sentinel skin cells. Rather than inhibiting, saliva enhanced production of certain pro-inflammatory mediators, such as IL-8 and IL-6.